Groundbreaking Solar Mission Faces Chilly Death

iamlucky13 writes "Over 17 years ago, the Ulysses spacecraft was launched aboard the space shuttle Discovery for a unique NASA/ESA mission. While nearly all other probes travel along our solar system's ecliptic plane, Ulysses used a Jupiter gravity assist to swing 80 degrees out of plane, carrying it over the sun's poles for an unprecedented view. During a mission that lasted four times longer than planned, it has flown through the tails of several comets, helped pinpoint distant gamma-ray bursts, and provided data on the sun and its heliosphere from the better part of two solar cycles. Unfortunately, the natural reduction of power from its radioisotope thermal generator means it is now unable to even keep its attitude control fuel from freezing, and NASA has decided to formally conclude the mission on July 1."

Comments

Re:I'd send it into the sun for one last splash

[cyclone96]

To change the orbit to intersect the sun, a tremendous amount of velocity would need to be removed from the current orbit. It would take more propellant to get it to the sun than it took to launch it from the earth in the first place.

It's actually quite difficult to "hit the sun", the Messenger spacecraft will need to do one earth, two Venus, and 3 Mercury flybys over 7 years to "slow down" enough so that it can finally brake into orbit around Mercury with it's insertion motor.

Re:I'd send it into the sun for one last splash

[u38cg]

Absolutely no way, is the short answer.

Long answer - in order to get it into the sun, you have to reduce its rotational velocity from numerous miles per second down to zero. You'll remember your 0.5mv^2 - that's how much calorific energy has to be in those tanks to achieve that. Also, at those kind of distances, almost any kind of rotational velocity will be enough to achieve orbit - meaning the damn thing will almost certainly miss and turn into a rather odd comet, which will no doubt baffle our ancestors.

Re:I'd send it into the sun for one last splash

[ozbird]

It doesn't carry anywhere near enough fuel for a sun dive.

Most of the energy to get into its current orbit came from its PAM-S and IUS solid rocket boosters, with Jupiter kicking it out of the ecliptic. Until New Horizons was launched recently, Ulysses was the fastest ever artificially-accelerated object - that's how much energy we're talking about. Ulysses started out with 33.5kg of hydrazine maneuvering fuel, and was down to 8.4kg in May 2002. In a nutshell, you could use up all of the remaining fuel and not get anywhere near the Sun (perhelion distance is around 1 AU.)

Re:RTG lifetime

[deglr6328]

Because the problem of failing RTGs is not due to radioactive decay. RTGs use Pu-238 which has a half life of 88 years. It's just as hot as when it launched. The problem is dopant migration in the semiconductor heterojunctiontions (peltier junctions) of the part that creates the electricity. They degrade over time and put out less electricity for the same reason an LED fails gradually over time slowly emitting less and less light for the same amount of energy put in.

Re:Mission's over?

[Anonymous Coward]

Did you see that big dish on it? "Floating around aimlessly" = not pointing at the earth. You can't transmit to the earth without attitude control.

Re:solar power?

[NathanBFH]

While this was certaintly true 17 years ago, it's interesting to note that we are now able to sufficiently power science craft with solar panels even as far as Jupiter. Check out Juno: http://en.wikipedia.org/wiki/Juno_(spacecraft)

Re:Don't know how to mod this

[jschen]

Definitely informative. Slowly failing RTG's due to degradation of the thermocouples that convert heat into electricity is a likely cause of the eventual end of the Voyager missions. More info at http://voyager.jpl.nasa.gov/spacecraft/spacecraftlife.html

Re:yeah but

[Tubal-Cain]

Ulysses was launched on October 6, 1990. Linux was announced August 25, 1991. (hurray for wikipedia!) Draw your own conclusions.

Re:The Real Ulysses

[Petrushka]

Yeah, because he sucked at navigation. Additionally, he was an idiot: All the things the gods warned him not to do because they would turn out to be bad, he did - and they went bad.

Not a single statement there accurately reflects the Odyssey. The actual story, as opposed to the one you've made up, relates that:

1. he took ten years because his men continually disobeyed his orders -- that's made clear in the first few lines --;
2. he shacked up with Circe for a year (voluntarily);
3. after he washed up on Calypso's island she basically held him prisoner for seven years. The story also relates how
4. any time a god told him to do something, he did exactly that; and
5. he is repeatedly described as having practically divine intelligence, and this is borne out by the various schemes he devises in the story. Even Athena compliments him on his deviousness.

The reason you do not understand his appeal to the ancient Greeks is because your memory of the story bears little resemblance to the actual story.

Here there's more

[Dusty]

The European Space Agency had a press conference about the end of Ulysses on Thursday. Brief note and audio feed. Longer press release.

The video the Ulysses Legacy has a great summary of the mission, and of the problems it now faces.